J.H. van Oostrom

MedCOM: a communication protocol to transmit physiologic data reliably over a modem connection

The authors designed and developed a communication protocol (MedCOM) specifically designed to transmit physiologic data over modem connections. MedCOM uses data packets of variable length, a checksum, and a positive acknowledge algorithm for reliability. MedCOM was tested with data generated by the Loral/UF Human Patient Simulator over a telephone link between Gainesville, FL and Orlando, FL. Link interruption tests show that MedCOM is reliable and that it has the ability to resynchronize a connection when synchronization is lost.

Interfacing existing medical monitoring equipment: a device driver approach

A method to interface with different physiological monitors is presented. Device-specific characteristics are implemented in device drivers in the form of Microsoft Windows DLLs (dynamic link libraries). A unified data representation is defined to make the application independent of the monitor providing the data.

Measurement of airflow through a metered dose inhaler during MRI

We designed, calibrated and tested a flow meter for use inside an MRI scanner for measuring airflow through a metered dose inhaler (MDI). Several flow measurement methods were analyzed and the differential pressure method was selected utilizing the inhaler as part of the sensor. Our system can measure respiratory flows during use enabling the relationships between flow rate, air flow resistance, inhaler design, and drug deposition to be measured.

Modeling the respiratory depressant effect of opioids: application to fentanyl

The respiratory depressant effect of fentanyl is described quantitatively by using a mathematical model. The model is an extension of a previous one reproducing the human ventilatory control system on physiological bases. The model includes three compartments (lung, body tissue and brain tissue), the main mechanisms involved in respiratory regulation (peripheral and central chemoreceptors, and the central hypoxic depression), and local blood flow regulation. Fentanyl effects on respiratory system include a weakening of the peripheral and central chemoreceptor gains on ventilation, a depression of body metabolism, and a direct inhibition of respiratory activity. All parameter values in the model have been chosen in accordance with clinical data from the literature. The model, with suitable values of its parameters, is able to reproduce the main respiratory variables in a wide range of fentanyl plasma concentrations, showing that minute ventilation in spontaneously breathing subjects depends on two antagonistic actions: opiod inhibitory influences, which abate ventilation, and the consequent chemoreflex stimulation. Simulations of resumption of spontaneous breathing after artificial ventilation in anesthetized patients indicate that a safe resumption can be achieved through approaches that increase patient CO/sub 2/ tension, since they shorten the time for chemoreceptor activation to overcome fentanyl-induced inhibition of respiratory activity.